Haeckel, 1862
Skeleton is composed of 20 radial spicules joined at proximal ends, bearing two concentric latticed shells each formed of 20 latticed plates. Distally, spicules may bear branched apophyses, which never form third shell. Endoplasm with pigments and zooxanthellae: genus Phractopelta.
Five species:
Phractopelta cruciata
Phractopelta dorataspis
Phractopelta histrix
Phractopelta stauropora
Phractopelta tessaraspis